Halogen anion-doped chromic oxide electrocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a halogen anion doped chromic oxide electrocatalyst and a preparation method and application thereof, and belongs to the technical field of new energy materials and electrochemical catalyst.The preparation method of the electrocatalyst comprises the steps that soluble chromium salt and polyvinylpyrrolidone are dissolved in a mannitol solution and then mixed with a soluble halogen salt solution, stirring is conducted, and the electrocatalyst is obtained; preparing to obtain a mixed solution; in a closed environment, heating the mixed solution at 160-180 DEG C for 6-24 hours to perform hydrothermal reaction, obtaining a reaction product after the reaction is finished, and then calcining in an air atmosphere to prepare the powdery halogen anion doped chromic oxide electrocatalyst, according to the method, the local structure, the spinning state, the energy band and the like of chromic oxide are regulated and controlled through the doped halogen anion ligand, the OER catalytic activity of the chromic oxide is optimized, the process is simple, and the method has good application prospects in the water electrolysis technology.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new energy materials and electrochemical catalysis, and particularly relates to a halogen anion doped chromium oxide electrocatalyst and a preparation method and application thereof. BACKGROUND

[0002] OER (Oxygen Evolution Reaction) reaction, namely oxygen evolution reaction, refers to a process of generating oxygen by water oxidation through the application of an electric potential in an electrochemical system. This reaction plays a crucial role in the fields of water splitting for hydrogen production, fuel cells, etc., and therefore, the research and development of OER reaction electrocatalysts are of great significance. Transition metal compounds are often used as OER reaction electrocatalysts, and compared with Co-based compounds and Ni-based compounds, the OER catalytic activity of chromium oxide is relatively poor, and it is usually used as a support material. The main reason for the low OER catalytic activity of chromium oxide is that the high energy barrier of water oxidation is caused by the electronic structure of Cr, and Cr2O3 is a Mott-Hubbard insulator with a larger charge transfer energy, resulting in a larger splitting energy.

[0003] In the prior art, chromium oxide is usually compounded with other materials to prepare OER reaction electrocatalysts. For example, the Chinese patent document with publication number CN115305481A discloses chromium oxide functionalized nickel-iron hydrotalcite nanosheets, and chromium oxide nanoparticles are deposited on the nickel-iron hydrotalcite nanosheets to form a heterostructure, wherein the chromium oxide nanoparticles are prepared by constant current technology. The heterostructure is in-situ grown on a nickel foam, denoted as Cr x O y -NiFe-LDH / NF; which can be used as a bifunctional electrocatalyst for anodic oxygen evolution reaction and cathodic hydrogen evolution reaction in electrolytic seawater and water. The Chinese patent document with publication number CN113604839A discloses a preparation method of a metal oxide passivated nickel / nickel oxide in-situ electrode. The invention first configures a precursor solution containing nickel / chromium (molybdenum) ions and nickel / chromium (molybdenum) oxides or nickel / chromium (molybdenum) hydroxides, attaches it to the surface of a nickel foam (NF), and then uses an electrochemical reduction method to apply a reduction potential in a specific electrolyte to reduce the nickel oxide or nickel hydroxide on the surface of the nickel foam (NF) to metal nickel, thereby obtaining a chromium oxide (molybdenum oxide) passivated nickel / nickel oxide in-situ electrode. The electrode exhibits excellent catalytic activity as a bifunctional electrocatalyst for hydrogen evolution reaction and oxygen evolution reaction. However, the above-mentioned methods cannot fundamentally solve the problem of low OER catalytic activity of chromium oxide.

[0004] It has been shown that the local spin states of ferromagnetic and antiferromagnetic under the influence of exchange coupling of CaMn3O4 clusters play an important role in the process of catalytic water splitting to produce triplet O2. Therefore, for the research and development of OER electrocatalysts, not only the local chemical structure needs to be studied, but also the local spin state needs to be adjusted, which is of great significance to improve the catalytic activity and understand the mechanism of oxygen evolution reaction. If the local structure and spin state of chromium oxide can be adjusted, and the energy band structure can be adjusted, it is expected to fundamentally solve the problem of low OER catalytic activity of chromium oxide. SUMMARY

[0005] In order to solve the problems existing in the prior art, the present application provides a halogen anion doped chromium oxide electrocatalyst, which adjusts the local structure, spin state, defect and energy band of the chromium oxide catalyst through the doped anion ligand, thereby optimizing the OER catalytic activity, and has low cost, simple preparation process, and good application prospect in water electrolysis technology.

[0006] The specific technical solutions adopted are as follows:

[0007] A preparation method of a halogen anion doped chromium oxide electrocatalyst, comprising the following steps:

[0008] (1) Dissolve the soluble chromium salt and polyvinylpyrrolidone in the mannitol solution, then mix with the soluble halogen salt solution, stir, and prepare a mixed solution;

[0009] (2) In a closed environment, the mixed solution is heated at 160-180 DEG C for 6-24 hours for hydrothermal reaction, and the reaction product is obtained after the reaction, and then calcined in air atmosphere, to prepare a powder of halogen anion doped chromium oxide electrocatalyst;

[0010] The soluble halogen salt is a soluble chloride salt or a soluble bromide salt, including sodium chloride or potassium bromide.

[0011] Optionally, the mixed solution of step (1) further contains carbon fiber cloth, and after the hydrothermal reaction and calcination step of step (2), a halogen anion doped chromium oxide electrocatalyst grown on the carbon cloth is prepared.

[0012] The present application prepares Cr2O3 corundum structure with antiferromagnetic and coplanar structure, and further, Br and Cl low field ligands are doped in the chromium oxide to adjust the local structure and spin state, reduce the charge transfer energy, increase the state density near the Fermi surface, and optimize the OER catalytic activity, wherein the Br doped Cr2O3 grown on the carbon cloth as an OER electrode shows the best catalytic activity and application potential.

[0013] Specifically, the soluble chromium salt is chromium nitrate nonahydrate, and the mass ratio of the soluble chromium salt to the polyvinylpyrrolidone is 1:0.5-1.2, and most preferably 1:1.

[0014] Preferably, the concentration of the mannitol solution is 0.05-0.5M, and further preferably 0.1M. The mannitol plays the role of a structure-directing agent and a Cr ion complex.

[0015] Specifically, the soluble halogen salt is preferably potassium bromide or sodium chloride, and the mass ratio of the soluble chromium salt to the soluble halogen salt is 1:1-10.

[0016] Preferably, the mixing solution is prepared by stirring sufficiently and intensively for at least 30min in step (1), which is beneficial to the doping of halogen anions.

[0017] Preferably, the mixing solution is transferred into a hydrothermal reactor, heated at 180℃ for 24 hours to perform a hydrothermal reaction, and after the hydrothermal reaction, the solid substance is separated and washed with deionized water for multiple times, and then dried to obtain the precursor.

[0018] Preferably, in step (2), the process parameters of the calcination process are as follows: calcination at 300-450℃ for 5-10 hours.

[0019] The application also provides the halogen anion-doped chromium oxide electrocatalyst prepared by the preparation method of the halogen anion-doped chromium oxide electrocatalyst.

[0020] The application also provides the application of the halogen anion-doped chromium oxide electrocatalyst in the oxygen evolution reaction of electrolysis water.

[0021] Compared with the prior art, the application has the following beneficial effects:

[0022] (1) The application dopes Br or Cl low-field ligands in the corundum structure of Cr2O3 to adjust the local structure and spin state thereof, reduce the charge transfer energy, increase the state density near the Fermi surface, and optimize the OER catalytic activity, thereby solving the problem of low OER catalytic activity of chromium oxide.

[0023] (2) The preparation method of the halogen anion-doped chromium oxide electrocatalyst is simple and efficient, and the raw material cost is low, and the catalyst exhibits excellent electrocatalytic activity and good stability for the OER reaction in an alkaline environment, and is expected to replace the noble metal catalyst and has a good application prospect in the water electrolysis technology. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1XRD patterns of different samples, wherein (a) is LaCrO3, (b) is CrO2, (c) is Cr2O3, (d) is Cl-Cr2O3, (e) is Br-Cr2O3, (f) is Cr2O3@CF and Br-Cr2O3@CF.

[0025] Figure 2 TEM and HRTEM images of different samples, wherein (a) and (e) are LaCrO3, (b) and (f) are CrO2, (c) and (g) are Cr2O3, (d) and (h) are Br-Cr2O3.

[0026] Figure 3 Raman spectra of different samples, wherein (a) is LaCrO3, CrO2, Cr2O3, Cl-Cr2O3 and Br-Cr2O3, (b) is Cr2O3@CF and Br-Cr2O3@CF.

[0027] Figure 4 XPS results of Br-Cr2O3 before and after etching, wherein (a) is XPS spectra of Br-Cr2O3 before and after etching, (b) is Cr 2p sub-peak region of Br-Cr2O3 before and after etching; (c) is O 1s sub-peak region of Br-Cr2O3 before and after etching; (d) is Br 3d sub-peak region of Br-Cr2O3 before and after etching.

[0028] Figure 5 OER performance characterization figures, wherein (a) is linear sweep voltammetry curves of LaCrO3, CrO2, Cr2O3, Cl-Cr2O3 and Br-Cr2O3; (b) is linear sweep voltammetry curves of Cr2O3@CF and Br-Cr2O3@CF; (c) is Tafel slope statistics figure; (d) is Nyquist figure of LaCrO3, CrO2, Cr2O3, Cl-Cr2O3 and Br-Cr2O3; (e) is Nyquist figure of Cr2O3@CF and Br-Cr2O3@CF; (f) is mass activity (MA) and specific activity (SA) statistics figure of LaCrO3, CrO2, Cr2O3, Cl-Cr2O3 and Br-Cr2O3. DETAILED DESCRIPTION

[0029] The application will be further described below in conjunction with the embodiments and drawings. It should be understood that these embodiments are only used to illustrate the application, and are not used to limit the scope of the application. The operation methods not specified in the following examples are usually carried out according to the conventional conditions, or according to the conditions recommended by the manufacturers. The contents not described in detail in the specification belong to the prior art known to those skilled in the art. The experimental materials used in the following examples can be purchased from the conventional biochemical reagent companies, unless otherwise specified.

[0030] Example 1

[0031] A mixture solution for hydrothermal reaction was prepared by dissolving chromium nitrate nonahydrate (0.4 g) and polyvinylpyrrolidone (0.4 g) in 25 ml of a mannitol (0.1 M) solution, then slowly adding the above mixture solution into 5 ml of deionized water containing KBr (3.25 g) and stirring vigorously for at least 30 minutes; the mixture solution was poured into a 100 ml Teflon-lined high-pressure reaction kettle and subjected to hydrothermal reaction at 180 °C for 24 hours, after which the hydrothermal reaction was completed, the precursor was separated by washing with deionized water multiple times and dried at 60 °C, and then calcined in an air atmosphere at 400 °C for 5 hours to obtain a halogen anion-doped chromium oxide electrocatalyst in the form of nanoparticles, denoted as Br-Cr2O3.

[0032] Example 2

[0033] A mixture solution for hydrothermal reaction was prepared by dissolving chromium nitrate nonahydrate (0.4 g) and polyvinylpyrrolidone (0.4 g) in 25 ml of a mannitol (0.1 M) solution, then slowly adding the above mixture solution into 5 ml of deionized water containing NaCl (1.59 g) and stirring vigorously for at least 30 minutes; the mixture solution was poured into a 100 ml Teflon-lined high-pressure reaction kettle and subjected to hydrothermal reaction at 180 °C for 24 hours, after which the hydrothermal reaction was completed, the precursor was separated by washing with deionized water multiple times and dried at 60 °C, and then calcined in an air atmosphere at 400 °C for 5 hours to obtain a halogen anion-doped chromium oxide electrocatalyst in the form of nanoparticles, denoted as Cl-Cr2O3.

[0034] Example 3

[0035] A mixture solution for hydrothermal reaction was prepared by dissolving chromium nitrate nonahydrate (0.4 g) and polyvinylpyrrolidone (0.4 g) in 25 ml of a mannitol (0.1 M) solution, then slowly adding the above mixture solution into 5 ml of deionized water containing KBr (3.25 g) and adding a piece of carbon fiber cloth (0.5 cm x 0.5 cm) and stirring vigorously for at least 30 minutes; the mixture solution was poured into a 100 ml Teflon-lined high-pressure reaction kettle and subjected to hydrothermal reaction at 180 °C for 24 hours, after which the hydrothermal reaction was completed, the precursor was separated by washing with deionized water multiple times and dried at 60 °C, and then calcined in an air atmosphere at 400 °C for 5 hours to obtain a halogen anion-doped chromium oxide electrocatalyst grown on carbon cloth, denoted as Br-Cr2O3@CF.

[0036] Comparative Example 1

[0037] LaCr03was synthesized using a two-step method: first, lanthanum nitrate hydrate (0.001 M) and chromium nitrate nonahydrate (0.001 M) were separately dissolved in 20 ml of deionized water and stirred for about 10 minutes to obtain a mixed nitrate solution; the mixed nitrate solution was slowly added to 20 ml of deionized water containing KOH (0.007 M). After stirring for 30 minutes, the mixture was transferred to a 100 ml Teflon-lined autoclave, and then hydrothermal reaction was carried out at 200°C for 24 hours. After the hydrothermal reaction, the precursor was separated by washing with deionized water several times and dried at 60°C, and then calcined at 800°C in an air atmosphere for 10 hours to obtain lanthanum chromite LaCr03.

[0038] Comparative Example 2

[0039] Chromium nitrate nonahydrate (0.4 g) and polyvinylpyrrolidone (0.4 g) were dissolved in 25 ml of a mannitol (0.1 M) solution, and a piece of carbon fiber cloth (0.5 cm x 0.5 cm) was added, and stirred vigorously for 30 minutes to prepare a mixture for hydrothermal reaction. The mixture was poured into a 100 ml Teflon-lined autoclave, and hydrothermal reaction was carried out at 180°C for 24 hours. After the hydrothermal reaction, the precursor was separated by washing with deionized water several times and dried at 60°C, and then calcined at 400°C in an air atmosphere for 5 hours to obtain Cr203@CF.

[0040] Comparative Example 3

[0041] Chromium nitrate nonahydrate (0.4 g) and polyvinylpyrrolidone (0.4 g) were dissolved in 25 ml of a mannitol (0.1 M) solution, and a piece of carbon fiber cloth (0.5 cm x 0.5 cm) was added, and stirred vigorously for 30 minutes to prepare a mixture for hydrothermal reaction. The mixture was poured into a 100 ml Teflon-lined autoclave, and hydrothermal reaction was carried out at 180°C for 24 hours. After the hydrothermal reaction, the precursor was separated by washing with deionized water several times and dried at 60°C, and then calcined at 400°C in an air atmosphere for 5 hours to obtain Cr203@CF.

[0042] Sample Analysis

[0043] In order to compare the samples prepared in the above examples and comparative examples, a commercial Cr02was directly purchased as a control sample, Figure 1 LaCr03(in (a) of Comparative Example 1), Cr02(in (b) of Comparative Example 1), Cr203(in (c) of Comparative Example 2), Cl-Cr203(in (d) of Example 2), Br-Cr203(in (e) of Example 1), and I-Cr203(in (f) of Example 1) were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), respectively. Figure 1 LaCr03(in (a) of Comparative Example 1), Cr02(in (b) of Comparative Example 1), Cr203(in (c) of Comparative Example 2), Cl-Cr203(in (d) of Example 2), Br-Cr203(in (e) of Example 1), and I-Cr203(in (f) of Example 1) were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), respectively. Figure 1 LaCr03(in (a) of Comparative Example 1), Cr02(in (b) of Comparative Example 1), Cr203(in (c) of Comparative Example 2), Cl-Cr203(in (d) of Example 2), Br-Cr203(in (e) of Example 1), and I-Cr203(in (f) of Example 1) were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), respectively. Figure 1 LaCr03(in (a) of Comparative Example 1), Cr02(in (b) of Comparative Example 1), Cr203(in (c) of Comparative Example 2), Cl-Cr203(in (d) of Example 2), Br-Cr203(in (e) of Example 1), and I-Cr203(in (f) of Example 1) were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), respectively. Figure 1 LaCr03(in (a) of Comparative Example 1), Cr02(in (b) of Comparative Example 1), Cr203(in (c) of Comparative Example 2), Cl-Cr203(in (d) of Example 2), Br-Cr203(in (e) of Example 1), and I-Cr203(in (f) of Example 1) were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), respectively. Figure 1XRD patterns of (a) LaCr03, (b) Cr02, (c) Cr203, (d) Cl-Cr203, (e) Br-Cr203, (f) Cr203@CF, and (g) Br-Cr203@CF in FIG. 1. Figure 1 The XRD patterns of (a) LaCr03, (b) Cr02, (c) Cr203, (d) Cl-Cr203, (e) Br-Cr203, (f) Cr203@CF, and (g) Br-Cr203@CF in FIG. 1.

[0044] The morphology and crystal structure of LaCr03in Comparative Example 1, purchased Cr02, Cr203in Comparative Example 2, and Br-Cr203in Example 1 were analyzed by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). For LaCr03, the TEM images showed that LaCr03exhibited spherical, elliptical, and some irregular particle morphologies with an average particle size of about 30 nm (FIG. 1(a)). The HRTEM images showed a lattice fringe spacing of about 0.27 nm (FIG. 1(b)), which is consistent with the (110) lattice fringe of LaCr03. Figure 2 Figure 2 The TEM images of Cr02showed that it exhibited rod-like morphology with flat surface and straight edges (FIG. 1(c)). The HRTEM images showed a lattice fringe spacing of about 0.24 nm (FIG. 1(d)), which is consistent with the (101) plane of Cr02. Figure 2 Figure 2 The TEM images of Cr02showed that it exhibited rod-like morphology with flat surface and straight edges (FIG. 1(c)). The HRTEM images showed a lattice fringe spacing of about 0.24 nm (FIG. 1(d)), which is consistent with the (101) plane of Cr02. Figure 2 Figure 2 ​​​In (g) and (h), the diamond structure pointing to the Cr2O3 phase in Br-Cr2O3 and Cr2O3 is (012).

[0045] The present inventors further investigated the elemental distribution of Cr2O3@CF and Br-Cr2O3@CF. EDS elemental mapping analysis revealed that Cr and O in Cr2O3@CF, and Cr, O, and Br in Br-Cr2O3@CF, were uniformly distributed throughout the fibers. The EDS image of Br-Cr2O3@CF revealed that Br accounted for 0.48% of the sample, further confirming the successful incorporation of bromine into the Cr2O3 lattice.

[0046] Figure 3 The Raman spectra of commercial CrO2 and samples prepared in Examples and Comparative Examples are shown. Figure 3 As shown in (a), for the LaCrO3 perovskite structure, 150.6 cm -1 and 175.8cm -1 The peak at 253-427 cm corresponds to the internal vibration of lanthanum. -1 The peak at 586 cm is associated with the octahedral rotation mode, while the peak at 586 cm -1 and 717cm -1 The peak at 452 cm is attributed to the bending and stretching vibrations of O-Cr-O. -1 (E g )、565.8cm -1 (A 2g ) and 575.96cm -1 (B 2g ) is attributed to CrO2. For Cr2O3 and Cl-Cr2O3, the peak at 306 cm -1 (E g )、344cm -1 (E g )、543cm -1 (A g ) and 599cm -1 (E g ) can be attributed to Cr 3+ (crystalline Cr2O3), and located at 1004cm -1 The peak at is attributed to Cr 6+ ; Located at 543cm -1 The Raman peaks near 553cm are related to the Cr-O lattice vibration, which is also found in LaCrO3 and CrO2. -1 The peak of Cr-O lattice stretching region can also be observed at 834 cm -1The peaks near the Br-O bond are attributed to the stretching of Br-O. Compared with Cr2O3, the Raman characteristic peak of Br-Cr2O3 is red-shifted, and the red shift may be related to the inductive effect of Br, because the presence of Br may change the internal stress and shorten the Cr-O bond. Figure 3 (b) shows the Raman spectra of Cr2O3@CF and Br-Cr2O3@CF, located at 1355 cm -1 and 1592cm -1 The broad peaks are the D band (disordered carbon) and G band (graphitic carbon) of carbon fibers. The strongest peaks of Cr-O lattice vibration (about 550 cm) can be seen in both Cr2O3@CF and Br-Cr2O3@CF. -1 ). The chromatin at 830 cm-1 can also be observed in Br-Cr2O3@CF. -1 There is a weak Br-O peak nearby.

[0047] In addition, the chemical compositions of LaCrO3, CrO2, Cr2O3, Cl-Cr2O3, and Br-Cr2O3 were analyzed by X-ray photoelectron spectroscopy (XPS). The results showed that the Cr 2p peaks of Cl-Cr2O3 and Br-Cr2O3 shifted toward lower binding energies compared to Cr2O3. This is likely due to the incorporation of Cl and Br elements, which have larger atomic radii and lower electronegativity relative to O atoms, thus altering the chemical environment surrounding the Cr atoms. Furthermore, the O1s peaks of Br-Cr2O3 and Cl-Cr2O3 shifted slightly toward lower binding energies compared to Cr2O3, likely due to the presence of bromine and chlorine. These peak shifts reflect changes in chemical bonding, and the corresponding results indicate that Cl and Br atoms were successfully incorporated into Cr2O3, resulting in the synthesis of Cl-Cr2O3 and Br-Cr2O3, respectively.

[0048] XPS etching experiments were performed on an Ar + The Ar of Br-Cr2O3 was studied on a gas cluster ion XPS system. + Etch the surface to explore the chemical environment changes of Cr, O and Br before and after etching (such as Figure 4 As shown in (a)-(d) in Figure 2), for Cr 2p, the fitting peak representing metallic Cr disappears after etching, while the Cr 3+ The fitted peak area of ​​Cr 3+ The content of Br2O3 increases after etching. For O1s, the O1s peak shifts to a higher binding energy after etching, which may be due to electron transfer from oxygen. For Br3d, the Br 3d peak is still visible after etching, but its intensity is weakened, indicating that Br elements are still present in the sample after etching. The presence of the Br 3d peak indicates that Br is not located on the sample surface, but has been successfully doped into the interior of Cr2O3.

[0049] Electrochemical measurements were all performed in 1.0 M KOH (pH = 14) electrolyte using a CHI760E electrochemical workstation and a three-electrode glass cell. Platinum wire was used as the counter electrode and the reference electrode was Ag / AgCl (saturated KCl). For powder (nanoparticle) samples, the electrocatalyst (8 mg), carbon black (1.6 mg) and 5% Nafion solution (50 μl) were dispersed in ethanol (4 ml) and sonicated for more than 1 hour to obtain a uniform electrocatalyst ink. The well-dispersed electrocatalyst was then transferred to a glassy carbon electrode (0.07 cm 2 ) on the electrocatalyst, the loading amount of the electrocatalyst was about 0.25 mg oxide cm -2 , and dried at 60 °C to test its performance. For carbon fiber samples, the electrocatalyst sample was fixed by an electrode clamp. The scan rate of linear sweep voltammetry (LSV) was 0.5 mVs -1 Electrochemical impedance spectroscopy (EIS) was performed at a voltage of 1.63 V, with a frequency range of 0.1 Hz to 100,000 Hz and an amplitude of 5 mV. Chronoamperometry (CP) was performed at 1.78 V.

[0050] like Figure 5 As shown in (a), Br-Cr2O3 exhibits higher electrocatalytic activity than other samples. In 1.0 M KOH solution, Br-Cr2O3 and Cl-Cr2O3 have a current density of 10 mA s at 1.61 V (vs RHE) and 1.64 V (vs RHE), respectively. -1 At a current density of 10 mA cm -2 When the overpotential of Br-Cr2O3 is 380mV, the overpotential of Cl-Cr2O3 is 410mV, which are lower than those of Cr2O3 (430mV), CrO2 (490mV) and LaCrO3. In 1.0M KOH solution, the current density of Br-Cr2O3@CF and Cr2O3@CF is 10mAs at 1.47V and 1.60V (vs RHE) respectively. -1 At a current density of 10 mA cm -2 When Br-Cr2O3@CF and Cr2O3@CF are 240mV and 370mV respectively. It can be clearly seen that Br-Cr2O3@CF has the lowest overpotential and the highest current density ( Figure 5 For LaCrO3, CrO2, Cr2O3, Cl-Cr2O3, and Br-Cr2O3, the current density was calculated by comparing it with the total mass loading of the catalyst (0.25 mg cm -2 ) and BET surface area normalization to compare mass activity (MA) and specific activity (SA). The results of MA and SA are shown in Figure 5The maximum MA value of Br-Cr2O3 was 289.5 mAmg at an overpotential of 520 mV -1 , and the maximum SA value was 0.99 mAcm -1 . In addition, as shown in (c) of Figure 5 , the Tafel slopes of the seven samples were also studied. The Tafel slope of Br-Cr2O3@CF was 54 mVdec -1 , while the Tafel slope of Cr2O3@CF was 65 mVdec -1 . The Tafel slopes of Br-Cr2O3, Cr2O3 and CrO2 were similar. The values of the Tafel slopes revealed more complex kinetic mechanisms. Electrochemical impedance spectroscopy (EIS) measurements were performed on the seven samples to study their charge transfer kinetics. The Nyquist plots showed that the charge transfer resistance of Br-Cr2O3 was the smallest (d) of Figure 5 , while the charge transfer resistance of Br-Cr2O3@CF was smaller than that of Cr2O3@CF (e) of Figure 5 . In addition, the catalytic stability of the catalysts was also an important factor. The long-term electrocatalytic stability of Cr2O3@CF and Br-Cr2O3@CF was studied by chronoamperometry at 1.70 V for 8 h. The stability test showed that the current density of Cr2O3@CF and Br-Cr2O3@CF decreased slightly, and the final current densities were 5.0 and 5.6 mAcm -2 , respectively.

[0051] The above-described embodiments have described the technical solutions of the present application in detail, and it should be understood that the above-described is only a specific embodiment of the present application, and is not used to limit the present application, and any modification, supplement or similar way of substitution made within the principle range of the present application should be included in the protection range of the present application.

Claims

1. A method for preparing a halogen anion-doped chromium oxide electrocatalyst, characterized in that: The following steps are involved: (1) dissolving a soluble chromium salt and polyvinyl pyrrolidone in a mannitol solution, and then mixing with a soluble halogen salt solution, stirring to prepare a mixed solution; (2) heating the mixture at 160-180° C. for 6-24 hours in a closed environment to perform a hydrothermal reaction, obtaining a reaction product after the reaction is completed, and then calcining the product in an air atmosphere to prepare a powdered halogen anion-doped chromium oxide electrocatalyst; The soluble halogen salt is a soluble chloride salt or a soluble bromide salt, including sodium chloride or potassium bromide.

2. The method for preparing the halogen anion-doped chromium oxide electrocatalyst according to claim 1, characterized in that: The mixed solution in step (1) also contains carbon fiber cloth. After the hydrothermal reaction and calcination steps in step (2), a halogen anion-doped chromium oxide electrocatalyst grown on the carbon cloth is prepared.

3. The method for preparing the halogen anion-doped chromium oxide electrocatalyst according to claim 1, characterized in that: The soluble chromium salt is chromium nitrate nonahydrate, and the mass ratio of the soluble chromium salt to polyvinyl pyrrolidone is 1:0.5-1.

2.

4. The method for preparing the halogen anion-doped chromium oxide electrocatalyst according to claim 1, characterized in that: The concentration of the mannitol solution is 0.05-0.5M.

5. The method for preparing the halogen anion-doped chromium oxide electrocatalyst according to claim 1, characterized in that: The soluble halogen salt is potassium bromide or sodium chloride, and the mass ratio of the soluble chromium salt to the soluble halogen salt is 1:1-10.

6. The method for preparing the halogen anion-doped chromium oxide electrocatalyst according to claim 1, characterized in that: When preparing the mixed solution in step (1), the stirring time is at least 30 minutes.

7. The method for preparing the halogen anion-doped chromium oxide electrocatalyst according to claim 1, characterized in that: In step (2), the process parameters of the calcination process are: calcination at 300-450° C. for 5-10 hours.

8. The halogen anion-doped chromium oxide electrocatalyst prepared according to the method for preparing the halogen anion-doped chromium oxide electrocatalyst according to any one of claims 1 to 7.

9. Use of the halogen anion-doped chromium oxide electrocatalyst according to claim 8 in oxygen evolution reaction by water electrolysis.

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